From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754733AbeCGPKR (ORCPT ); Wed, 7 Mar 2018 10:10:17 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58458 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754608AbeCGPKO (ORCPT ); Wed, 7 Mar 2018 10:10:14 -0500 Subject: Re: [PATCH] KVM: VMX: expose the host's ARCH_CAPABILITIES MSR to userspace To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Cc: Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, David Woodhouse , KarimAllah Ahmed References: <1519433546-33879-1-git-send-email-pbonzini@redhat.com> <20180226221300.GK22024@char.us.oracle.com> <20180301213205.GB29001@flask> <20180302214212.GB13606@flask> <9cad32c8-fdb6-95db-2cd3-a0e3297b1811@redhat.com> <20180307145628.GA12299@flask> From: Paolo Bonzini Message-ID: <37a89c09-e933-9256-1b7a-3a9df846a672@redhat.com> Date: Wed, 7 Mar 2018 16:10:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180307145628.GA12299@flask> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/03/2018 15:56, Radim Krčmář wrote: > The MSR_F10H_DECFG default is questionable -- MSR_F10H_DECFG is an > architectural MSR, so we'd be changing the guest under the sight of > existing userspaces. > A potential security risk if they migrate the guest to a CPU that > doesn't serialize LFENCE. ARCH_CAPABILITIES are at least hidden by a > new CPUID bit. Good point. Perhaps we should add a KVM-specific CPUID bit for serializing LFENCE. > The feature MSR defaults are going to be a mess anyway: we have > MSR_IA32_UCODE_REV that is tightly coupled with CPUID. Not a good > candidate for passing by default and currently also has a default value. Yeah, ucode revision is out of question. Paolo